Does anyone now a general rule on how slow a vfd can power an induction motor without overheating or damaging the motor itself? We use vfd's on cooling fans and we usually limit their speed to at least 20%. We had a situation where recently the cutler hammer vfd was shutting the motor down due to overheating (somehow the vfd sensed this). The speed limit was not installed so I am assuming that is the reason for this. Thanks